A study has been made of cerebral blood flow (CBF) in gerbils by laser Doppler velocimetry (LDV). The gerbils were subjected to repeated bilateral carotid occlusions and studied for up to 3 hours. Continuous measurement of the CBF was made of both parietal cortices simultaneously using 2 probes separately located. The purpose of these experiments was to examine the agreement between the two sides. The essential finding was that while the CBF dynamics were usually similar, they were not always the same and the differences could be substantial in time of recovery, magnitude of recovery and in pattern of recovery.